What's a heart murmur?

Noise. It's a subjective finding of noise in a heart by stethoscope. Some murmurs are physiologically normal and others require further evaluation by echocardiogram.
Murmur. A murmur is a noise caused by turbulent flow in a vessel or the heart. Anemia often causes an increased heart rate which can cause a murmur. Abnormal valves or connections between chambers can also cause murmur.